The present invention relates to a highly durable electrophotographic photoreceptor which minimizes wear and damage of the surface layer during repeated image-forming processes, and fatigue degradation due to incomplete cleaning, etc.
In order to carry out image formation employing an electrophotographic method, the surface of an electrophotographic photoreceptor is charged, exposed imagewise and developed to form a toner image. The toner image is transferred onto a transfer material and fixed to form an image. The photoreceptor which has completed the image transfer is subjected to cleaning and discharging, and is repeatedly employed.
The above-mentioned photoreceptor is required to exhibit excellent electrophotographic properties such as charging potential, sensitivity, residual potential, etc.; in addition to these, physical properties such as long printing life, wear, moisture, etc. during repeated usage, and resistance against ozone, generated by corona discharging and image exposure.
It is commonly assumed that the fatigue-caused degradation of electrophotographic properties of a photoreceptor during the repeated usage is caused by the wear and damage to the surface layer of the photoreceptor during each process such as transfer of toner images formed on the photoreceptor to transfer materials, separation, cleaning of residual toner from the photoreceptor after the transfer, and film formed by hygroscopic substances such as toner, paper dust, etc.
Conventionally, for the above-mentioned photoreceptors, there have been widely employed inorganic photoreceptors, comprising inorganic photoconductive materials, and organic photoreceptors, comprising organic photoconductive materials.
The organic photoreceptors are those prepared by coating, on a conductive support, a photosensitive composition prepared by dissolving or dispersing an organic photoconductive material in a solvent, together with a binder, if desired. Particularly, a function-separated type photoreceptor is practically important in which the charge generating function and the charge transport function are performed by different materials. As the function-separated type photoreceptors, many photoreceptors are employed which specifically comprise a charge generating layer comprising a charge generating material, and a charge transport layer comprising a charge transport material.
The surface of a photoreceptor, prepared by coating an organic or inorganic photoconductive material employing a solvent, is soft compared to a photoreceptor prepared by depositing inorganic photoconductive materials such as selenium, amorphous silicone, etc. employing vaporization, glow discharge, etc., and results in disadvantages such as being susceptible for the increased wear and damage during repeated usage and film formed by hygroscopic materials due to incomplete cleaning. On account of this, improvement in physical properties of the surface layer of the photoreceptor is much in demand.
For example, in Japanese Patent Publication Open to Public Inspection No. 5-113670, a method to prevent the formation of film made by toner, paper dust, etc. is proposed in which siloxane-copolymerized polycarbonate is incorporated into the surface layer of a photoreceptor as a binder resin to make the surface layer of the photoreceptor lubricant and to improve the cleaning properties, and in Japanese Patent Publication Open to Public Inspection No. 4-368953, fine particles of fluoro-resin are incorporated into the surface layer of a photoreceptor in order to obtain the same effects as above.
In Japanese Patent Publication Open to Public Inspection No. 3-155558, a method to improve wear resistance of the surface of a photoreceptor is proposed in which fine inorganic particles such as silica, tin oxide, etc. are incorporated into the surface layer of the photoreceptor.
As a solvent for the inorganic photoreceptor which is prepared by coating a photosensitive composition comprising the above-mentioned inorganic photoconductive material, toluene, tetrahydrofuran, dioxane, methyl ethyl ketone, cyclohexane, etc. have been employed. However, these solvents exhibit poor solubility for binder resins employed for an organic photoreceptor comprising an organic photoconductive material. Instead of these, halogenated solvents such as methylene chloride, ethylene chloride, chloroform, monochlorobenzene, etc. are mainly employed. The halogenated solvents exhibit good solubility and coating properties for binder resins of an organic photoreceptor such as polycarbonate, polyacrylate, etc.
In the photoreceptor which is prepared by coating a photosensitive composition comprising the above-mentioned inorganic or organic photoconductive material, a part of the solvent inevitably remains in the photosensitive layer during the drying process following coating. This remaining solvent lowers or deletes improvements in wear resistance and degrades cleaning properties of the surface layer of the photoreceptor described, for example, in the above-mentioned references, and when image formation is repeated employing the photoreceptor, it is subjected to fatigue degradation due to wear and damage of the surface layer of the photoreceptor, incomplete cleaning, etc., which result in defective images due to the decrease in image density and formation of background staining.
The above-mentioned halogenated solvents require decreased usage amounts due to environmental pollution and possible carcinogenicity.
By employing dioxolan or a derivative as a solvent for a photosensitive composition, it was found that excellent solubility or dispersing properties is exhibited for photoconductive materials and binder resins and in addition, causes no environmental pollution, carcinogenicity, or ozone depletion. Furthermore, when the optimum amount of dioxolan or the derivative remains in the photosensitive layer, improvements in wear resistance and cleaning properties are further enhanced.
An object of the present invention is to provide a photoreceptor which exhibits improvements in wear resistance and cleaning properties, minimum fatigue degradation during the repeated image-forming process employing the above-mentioned photoreceptor repeatedly, no formation of background staining over an extended period, and stably produces clear images of high density.
The photoreceptor of the present invention and its embodiment are described.
The electrophotographic photoreceptor of the present invention comprises an conductive support having thereon a photosensitive layer, and the surface layer of the photoreceptor comprises binder resin having silicon or fluorine atoms and dioxolan or a derivative thereof at 0.001 to 10 weight percent.
The surface layer may preferably comprise fine organic particles. The fine organic particles are preferably a compound comprising fluorine.
The surface layer may preferably comprise fine inorganic particles. The fine inorganic particles are preferably oxides of silicon or tin.
The surface layer of the photoreceptor may comprise both of fine inorganic and organic particles. The fine organic particles preferably comprise fluorine atoms and fine inorganic particles are preferably oxides of silicon or tin.
The surface layer preferably contains silicone oil.
The electrophotographic photoreceptor comprises an conductive support having thereon a photosensitive layer and the surface layer of the photoreceptor comprises fine organic particles and dioxolan or a derivative thereof at 0.001 to 10 weight percent.
These fine organic particles are preferably a compound comprising fluorine atoms.
The surface layer of this photoreceptor preferably comprises a binder resin having silicon or fluorine atoms.
An electrophotographic photoreceptor comprises an conductive support having thereon a photosensitive layer and the surface layer of the photoreceptor comprises fine inorganic particles and dioxolan or a derivative thereof at 0.001 to 10 weight percent.
The fine inorganic particles are preferably oxides of silicon or tin.
The surface layer of the photoreceptor preferably comprises a binder resin having silicon or fluorine atoms.
The electrophotographic photoreceptor compries an conductive support having thereon a photosensitive layer and the surface layer of the photoreceptor comprises fine inorganic and organic particles, and dioxolan or a derivative thereof in 0.001 to 10 weight percent.
The fine organic particles preferably comprise fluorine atoms and fine inorganic particles are preferably oxides of silicon or tin.
The surface layer of the photoreceptor preferably contains silicone oil.
The present invention is further detailed below.
Incorporated into the surface layer of a photoreceptor, are a binder resin comprised of silicon or fluorine atoms which makes the surface layer lubricant and also comprised of fine organic particles and/or fine inorganic particles intended to make the surface layer wear resistant. Along with the above-mentioned resin and particles, dioxolan or a derivative thereof is employed as a solvent for the coating composition to form the surface layer of the photoreceptor, and further 0.001 to 10 weight percent of the dioxolan or a derivative thereof is incorporated into the dried surface layer of the photoreceptor.
The photoreceptor comprises an inorganic photoconductive material or organic photoconductive material in its binder resin. The organic photoreceptor is mainly explained below.
Binder resins containing silicon or fluorine atoms, which are incorporated into the surface layer of the photoreceptor include those mentioned below.
(Binder Resins Comprising Silicon Atoms)
These resins include siloxane-carbonate block-copolymers and siloxane-ester block-copolymers described on pages 5 and 6 of Japanese Patent Publication Open to Public Inspection No. 3-171056; the siloxane-carbonate block-copolymers described on pages 5 to 7 of Japanese Patent Publication Open to Public Inspection No. 5-113670, and the siloxane-carbonate block-copolymers described on pages 11 to 14, 16 to 20, 23 to 32, and 35 to 37 of Japanese Patent Publication Open to Public Inspection No. 8-87119.
Siloxane-ester Block-Copolymers: 
wherein R represents an alkylene group having from 3 to 20 carbon atoms; A represents an alkylene or arylene group having from 2 to 20 carbon atoms; R1 and R2 each represents an alkyl group having from 2 to 10 carbon atoms, or R2 represents an alkyl group, an aralkyl group, an alkaryl group or an aryl group; xe2x80x9caxe2x80x9d represents 10 to 200; xe2x80x9cbxe2x80x9d represents 1 to 25; xe2x80x9ccxe2x80x9d represents 5 to 20; xe2x80x9cdxe2x80x9d represents 2 to 1,000. In the above-mentioned structural formula, A represents phenylene or bisphenylnene preferably comprising the following formula: 
wherein R3 and R4 each represents a hydrogen atom or an alkyl group, a substituted alkyl group, an aryl group, an anthracenyl group, a substituted aryl group, or R3 and R4 form a single ring, double ring, or heterocyclic group together with bonding carbon atoms. R5, R6, R7, and R8 each independently represents a hydrogen atom, or a halogen atom, or an alkyl group, a substituted alkyl group, an aryl group, or a substituted aryl group.
Siloxane-bisphenolcarbonate Block-Copolymers: 
wherein R1, R2, R3, R4, R5, R6, R7, and R8 each represents a hydrogen atom, a halogen atom, a lower alkyl group; X represents xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SO2xe2x80x94 bonding group, and an alkylene group, and R9 and R10 each represents a lower alkyl group; m/(m+n) is 0.2 to 0.8.
A represents 
xe2x80x94Sxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94 or xe2x80x94(CH2)w, or direct bonding is allowed without A.
wherein R1, R2, R3, R4, R5, R6, R7, and R8 each represents a hydrogen atom, a halogen atom, a lower alkyl group; w represent an integer of 2 or more; Ra and Rb each represents a hydrogen atom, a substituted or unsubstituted alkyl or aryl group, or represent a group of atoms necessary for forming a carbon ring or heterocyclic ring upon combining with each other; Rc and Rd each represents a substituted or unsubstituted alkyl or aryl group. p and q represent a number which satisfies the relation of p/(p+q)=0.1 to 0.9. R9 represents an alkylene or alkylidene having from 2 to 6 carbon atoms; R10, R11, R12, and R13 each represents an alkyl group having from 1 to 3 carbon atoms, a phenyl group, or a substituted phenyl group; n represents an integer of 1 to 200.
(Binder Resins Comprising Fluorine Atoms)
These resins include, for example, carbonate-fluorine-substituted paraffin block-copolymers described on page 3 of Japanese Patent Publication Open to Public Inspection No. 3-45958 and also polycarbonates having a fluorine substituent described on pages 2 to 4 of Japanese Patent Publication Open to Public Inspection No. 5-188628.
Combination of a main segment polymer (hereinafter referred to as xe2x80x9cAxe2x80x9d) and a fluorine atom containing segment polymer (hereinafter referred to as xe2x80x9cBxe2x80x9d):
Combinations of A and B are optional such as A-B, A-B-A, A-B-A-B, etc., and the ratio is not particularly limited.
Specific examples of representative combinations of A and B are illustrated below.
xe2x80x9cAsxe2x80x9d include methacryl series polymers such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polyhexyl methacrylate, polydecyloctyl methacrylate, polystearyl methacrylate, etc.; acryl series polymers such as polymethyl acrylate, polyethyl acrylate, polybutyl acrylate, poly-2-ethylhexyl acrylate, polymethoxyethyl acrylate, etc.; vinyl acetate series polymers such as polyvinyl acetate, vinyl acetate ethylene copolymers, etc.; styrene series polymers such as polystyrene, chloromethylated polystyrene, styrene-butadiene copolymers, styrene-methacrylate copolymers, etc.; polycarbonate series polymers such as representative examples mentioned below.
Structural Formula (1) of Polycarbonate Series Polymers 
Structural Formula (2) of Polycarbonate Series Polymers 
Structural Formula (3) of Polycarbonate Series Polymers 
Structural Formula (4) of Polycarbonate Series Polymers 
Structural Formula (5) of Polycarbonate Series Polymers 
Structural Formula (6) of Polycarbonate Series Polymers 
Structural Formula (7) of Polycarbonate Series Polymers 
xe2x80x9cAsxe2x80x9d further include polyester series polymers such as unsaturated polyesters composed of styrene, maleic acid, ethylene glycol, phthalic acid, etc., alkyd resins composed of phthalic acid, glycols, etc.
As xe2x80x9cBxe2x80x9d, fluorine-substituted paraffin series polymers are employed.
Representative examples include polyvinylidene fluoride, polyvinyl fluoride, ethylene-tetrafluoroethylene copolymers, tetrafluro-hexafuoropropylene copolymers, etc.
Polycarbonates comprising a terminal structure represented by the following formula;
xe2x80x94Arxe2x80x94(R)mxe2x80x94Rf 
wherein Ar represents an aryl group which is allowed to have a substituent; m represents an integer of 0 or 1; R represents an alkyl group, an oxygen atom, an sulfur atom, xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94NHxe2x80x94COxe2x80x94 and a combination of two of these or more; Rf represents a long chain fluorinated alkyl group.
Specifically, Ar represents 
wherein Y represents a methyl group, a chlorine atom, a bromine atom, a fluorine atom, an iodine atom, a cyan group, a trifluoromethyl group, a nitro group or a hydrogen atom. 
Rf represents xe2x80x94(CF2)7xe2x80x94CF3, xe2x80x94(CF2)9xe2x80x94CF3, xe2x80x94(CF2)11xe2x80x94CF3, xe2x80x94(CF2)13xe2x80x94CF3, xe2x80x94(CF2)15xe2x80x94CF3, xe2x80x94(CF2)17xe2x80x94CF3, 
R represents xe2x80x94CH2xe2x80x94, xe2x80x94CH2CH2xe2x80x94, xe2x80x94Oxe2x80x94CH2xe2x80x94, xe2x80x94Oxe2x80x94CH2xe2x80x94CH2xe2x80x94, xe2x80x94COxe2x80x94CH2xe2x80x94, xe2x80x94COxe2x80x94CH2xe2x80x94CH2xe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94CH2xe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94CH2xe2x80x94CH2xe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94CH2xe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94CH2xe2x80x94CH2xe2x80x94, xe2x80x94COxe2x80x94NHxe2x80x94CH2xe2x80x94CH2xe2x80x94, xe2x80x94COxe2x80x94NHxe2x80x94CH2xe2x80x94CH2xe2x80x94, xe2x80x94NHxe2x80x94COxe2x80x94CH2xe2x80x94, xe2x80x94NHxe2x80x94COxe2x80x94CH2xe2x80x94CH2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94NHxe2x80x94COxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SO2xe2x80x94
xe2x80x94Arxe2x80x94(R)mxe2x80x94Rf represents; 
The content amount of the above-mentioned binder resin comprising silicon or fluorine atoms in the surface layer of the photoreceptor is preferably 0.1 weight percent or more, and more preferably 1 weight percent or more of the resin in the above-mentioned surface layer. When the content amount is not more than 0.1 weight percent, insufficient lubricating properties are provided, and further, during image formation, incomplete cleaning is exhibited.
Fine organic particles and fine inorganic particles which can be incorporated into the surface layer of the photoreceptor include these mentioned below.
Examples of the fine organic particles include polytetrafluoroethylene, polyvinylidene fluoride, polyethylene chloride trifluoride, polyvinyl fluoride, polyethylene tetrafluoride-perfluoroalkylvinylether copolymer, polyethylene tetrafluoride-propylene hexafluoride copolymer, polyethylene-trifluoride ethylene copolymer, polyethylene tetrafluoride-propylene hexafluoride-perfluoroalkylvinylether copolymer, polyethylene, polyvinyl chloride, metal stearate salt, polymethylmethacrylate or melamine. The volume average diameter of the fine organic particles is preferably between 0.05 and 10 xcexcm. The amount of fine organic particles incorporated into the surface layer of the photoreceptor is preferably between 0.1 and 100 weight percent of the binder resin in the surface layer, and more preferably between 1 and 50 weight percent, so that the photosensitive layer is provided with sufficient lubricating properties to prevent incomplete cleaning and to obtain the preferred sensitivity and minimal background staining.
Examples of fine inorganic particles include metal oxides such as magnesium oxide, calcium oxide, titanium oxide, zirconium oxide, tin oxide, aluminum oxide, silicon oxide (silica), indium oxide, beryllium oxide, lead oxide, and bismuth oxide; nitrides such as boron nitride, aluminum nitride, and silicon nitride, and carbides such as silicon carbide and boron carbide. Fine inorganic particles are preferably subjected to hydrophobic treatment employing hydrophobic processing agents such as titanium coupling agents, silane coupling agents, aluminum coupling agents, high molecular fatty acids, etc.
The volume average particle diameter is preferably between 0.05 and 2 xcexcm. Furthermore, in order to provide sufficient mechanical strength with the surface layer of the photoreceptor and to minimize wear and damage of the surface layer of the photoreceptor during the image formation, and incomplete cleaning, the amount of the above-mentioned fine inorganic particles is preferably between 0.1 and 100 weight percent, and more preferably between 1 and 50 weight percent of the binder resin of the above-mentioned surface layer. Further, the volume average particle diameter of fine organic and inorganic particles is measured by, for example, a laser diffraction/scatter type particle size distribution measuring apparatus xe2x80x9cLA-700xe2x80x9d (manufactured by Horiba Seisakusho Co.).
Dioxolan or a derivative thereof are explained.
(Dioxolan or Dioxolan Derivative)
Dioxolan or dioxolan derivative is a cyclic 5-member ether compound and compound having a dioxolan nucleus comprising two oxygen atoms which are not adjacent to each other in the molecule. Specifically, those represented by formula (1) are preferably employed. 
wherein R1 to R6 each represents a hydrogen atom or a substituted or unsubstituted alkyl group having from 1 to 6 carbon atoms. R5 and R6, or at least two groups of R1 to R4 may combine with each other to complete a ring. R1 to R6 each is preferably a hydrogen atom or a substituted or unsubstituted alkyl group having from 1 to 4 carbon atoms. The substituent of the alkyl group includes preferably an alkoxy group having from 1 to 4 carbon atoms, an acyl group, an acyloxy group or a hydroxyl group. Examples of rings which are formed by combining R5 and R6, or at least two groups of R1 to R4, are optional. However, they are preferably 5- to 6-member aromatic rings (for example, a benzene ring) or non-aromatic rings (for example, a cyclohexane ring).
Of these, any of R1 to R6 is preferably a hydrogen atom and further, all R1 to R6 are preferably hydrogen atoms.
The boiling point of dioxolan or a dioxolan derivative is preferably between 70 and 200xc2x0 C. under normal pressure; more preferably 150xc2x0 C. or lower, and most preferably between 70 and 130xc2x0 C.
By employing compounds having the preferred boiling point, the optimum amount of dioxolan or a dioxolan derivative can be incorporated into the surface layer of the photoreceptor employing optimum drying time and thus a uniform coating layer is readily prepared and electric potential during repeated usage is stably maintained.
Specific compound examples are illustrated below. 
Generally, a photoreceptor is formed in such a way that a subbing layer is provided, if desired, on a conductive support and on the subbing layer, a charge generating layer and a charge transport layer in this order are provided. The charge transport layer is prepared by coating and drying, on the charge generating layer, a coating solution obtained by dissolving a charge transport material and a binder resin to a solvent comprising dioxolan or a dioxolan derivative. Dioxolan or a dioxolan derivative can be incorporated into the charge transport layer by coating and drying the coating solution to form the charge transport layer.
In order to improve cleaning properties of the surface layer of a photoreceptor (herein, a charge transport layer) and wear resistance, and to minimize background staining caused by an increase in residual electric potential during the image formation, the amount of dioxolan or a dioxolan derivative in the charge transport layer is between 0.001 and 10 weight percent of the charge transport layer.
As solvents for the charge transport layer, when dioxolan or a dioxolan derivative is employed in combination with other solvents, are those employed which are excellent in compatibility with dioxolan or a derivative thereof and exhibit high solubility to a binder resin.
(Constitution of the Photoreceptor)
((Photosensitive Layer))
The photoreceptor of the present invention is preferably one in which, on a conductive support, a photosensitive layer comprising an organic photoconductive material is provided, and an organic photoreceptor is particularly preferred in which a charge generating layer comprising a charge generating material and a charge transport layer comprising a charge transport material are formed in this order.
The charge generating layer is prepared by dispersing a charge generating material into a binder resin, if desired. Charge generating materials include metal or metal-free phthalocyanine compounds, azo compounds such as bisazo compounds, trisazo compounds, squarium compounds, azulenium compounds, perylene series compounds, indigo compounds, quinacridone compounds, polycyclic quinone series compounds, cyanine dyes, xanthene dyes, charge transfer complexes consisting of poly-N-vinylcarbazole, trinitrofluorenone, etc. Particularly, are those preferred which are imidazole perylene compounds, one type of perylene compounds exhibiting excellent photoconductive properties and metal phthalocyanine compounds such as titanyl phthalocyanine, gallium phthalocyanine, or hydroxygallium phthalocyanine.
Binder resins which can be employed in the charge generating layer include, for example, polystyrene resins, polyethylene resins, polypropylene resins, polyacryl resins, polymethacryl resins, polyvinyl chloride resins, polyvinyl acetate resins, polyvinyl butyral resins, polyepoxy resins, polyurethane resins, polyphenol resins, polyester resins, polyalkyd resins, polycarbonate resins, polysilicone resins, polymelamine resins, and copolymer resins comprising at least two repeating units or more of these resins such as, for example, vinyl chloride-vinyl acetate copolymer resins, vinyl chloride-vinyl acetate-maleic acid unhydride copolymer resins, or high molecular organic semiconductors such as, for example, poly-N-vinylcarbazole, etc.
The charge transport layer, composed of single charge transport material together, generally, with a binder resin, is provided on the charge generating layer. The charge transport materials include, for example, carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, pyrazoline derivatives, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, benzidine derivatives, poly-N-vinylcarbazole, poly-1-vinylpyrene, poly-9-vinylanthracene, etc. These charge transport materials may be employed individually or in combination of two or more.
The charge transport layer is generally composed of the surface layer of a photoreceptor. As the binder resins, mainly employed are silicon atom-containing resins such as siloxane-ester block-copolymers or siloxane-carbonate block-copolymers, etc. described in the above-mentioned Japanese Patent Publication Open to Public Inspection Nos. 3-171056, and 5-113670, and particularly, 8-87119. In addition, mainly employed are fluorine atom-containing polycarbonate resins described in the above-mentioned Japanese Patent Publication Open to Public Inspection Nos. 3-45958 and 5-188638. Other resins mentioned below may be incorporated at about 50 weight percent or less, if desired.
When fine organic particles and/or fine inorganic particles are incorporated into the surface layer of a photoreceptor, other binder resins mentioned below may be employed as a main component. At that time, the polycarbonate series resins mentioned below are preferably employed.
Other resins include, for example, polycarbonates (bisphenol A type polycarbonates, bisphenol Z type polycarbonates), polycarbonate series copolymers, polyester, polyurethane, polystyrene, polystyrene series copolymers, polysiloxane, polyacrylate, polyacrylate series copolymers, phenoxy resins, ABS resin, polyvinyl chloride, polyvinyl chloride series copolymers, polyvinyl acetate series copolymers, polyvinyl formal or polyvinyl butyral, etc.
Particularly preferred conditions of the present invention are that the above-mentioned silicon atom- or fluorine atom-containing binder resin is employed in the surface of a photoreceptor, and further, the above-mentioned fine organic and/or fine inorganic particles are incorporated and in addition, dioxolan or dioxolan derivative of 0.001 to 10 weight percent is incorporated. Utilizing these synergetic effects, photoreceptors can be prepared which exhibit excellent cleaning properties and wear resistance.
Silicone is preferably incorporated into the photosensitive layer, especially into the charge transport layer of the photoreceptor of the present invention.
In addition to the fact that the above-mentioned silicone oil flattens and smoothes the coated surface, it is found that a dioxolan compound incorporated into the photosensitive layer results in the preferred effect. Nitrogen oxides generated during charging are considered to deteriorate the sharpens of images, however, the addition of silicone oil decreases the deterioration in sharpness. Furthermore, the addition of silicone oil is found to prevent the degradation of image quality during operation of numerous sheets.
Silicone oil is dissolved in a dioxolan compound and added to compositions constituting a photosensitive layer.
Preferred silicone oils are those described in Japanese Patent Publication Open to Public Inspection Nos. 54-143643, 57-5050, 57-212453, 59-208556, 63-80262, 1-234854, 4-199154, 5-27456, etc. Particularly, methylphenyl silicone oil and dimethyl silicone oil are preferred, and the added amount is preferably between 10 and 1,000 ppm in the solid portion of the incorporated layer.
Examples of silicone oils are shown below. 
wherein R represents a hydrogen atom, an alkyl group having from 1 to 3 carbon atoms, an alkoxy group having from 1 to 3 carbon atoms, a phenyl group, an alkylphenyl group, an oxyethyl group, an oxypropyl group; m represents an integer of 0 to 2.000, and n represents an integer of 0 to 2.000.
Specifically, included are dimethylsilicone oil (SH200, manufactured by Toray Silicone Co.; KF96, manufactured by Shin-Etsu Kagaku Kogyo Co.; TSF451, manufactured by Toshiba Silicone Co.) and methylphenylsilicone oil (SH510, manufactured by Toray Silicone Co.; KF50, manufactured by Shin-Etsu Kagaku Kogyo Co.; TSF431, manufactured by Toshiba Silicone Co.). Those in which R in the above-mentioned general formula is modified with a functional group are employed such as alkyl-modified silicone, alkylaryl-modified silicone, alkoxy-modified silicone, alcohol-modified silicone, amine-modified silicone, oxyalkyl-modified silicone, fluorine-modified silicone, glycol-modified silicone, polyether-modified silicone, fatty acid ester-modified silicone, etc.
Specific examples are shown below. 
Selected as silicone oil incorporated into the above-mentioned charge transport layer and charge generating layer according to the present invention are, for example, alkylslicone oil, arylsilicone oil, alkylarylsilicone oil, etc. Methylphenyl silicone oil is excellent, and one having a content ratio of the phenyl group of 10 to 25 percent is particularly excellent. Such silicone oils are commercially available, and KF-50, KF-54, and KF-56, manufactured by Shin-Etsu Kagaku Kogyo Co., and TSF431, TSF443, and TSF437, manufactured by Toray Silicone Co., etc., for example, are preferably employed.
In order to minimize fatigue degradation during repeated usage of a photoreceptor or to improve the durability, incorporated into any layer constituting the photosensitive layer of the photoreceptor, may be if desired, the optimum added amount of ambient dependence-minimizing agents such as antioxidants, electron accepting materials, surface improving agents, plasticizers, etc., known in the art.
Examples of antioxidants preferably employed include, for example, those having a hindered-amine structure unit or a hindered-phenol structure unit, or those having both, organic phosphorus series compounds, organic sulfur series compounds, hydroquinone series compounds, phenylamine series compounds, etc.
(1) Exemplified Compounds Having a Hindered-Phenol Structure Unit 

(2) Exemplified Compounds Having Hindered-Amine Structure Unit and a Hindered-Phenol Structure Unit 
(3) Exemplified Compounds Having a Hindered-Amine Structure Unit 
(4) Examples of Phosphorous Series Compounds
These are compounds, for example, represented by general formula ROxe2x80x94P(OR)xe2x80x94OR, wherein the Rs each represents a hydrogen atom, or a substituted or unsubstituted alkyl, alkenyl or aryl group. Representative compounds include the following: 
(5) Organic Sulfur Series Compounds
These are compounds, for example, represented by general formula Rxe2x80x94Sxe2x80x94R, wherein each R represents a hydrogen atom, or a substituted or unsubstituted alkyl, alkenyl or aryl group. The representative compounds include the following: 
(6) Hydroquinone Series Compounds
Hydroquinone series compounds include, for example, compounds represented by the general formula below. 
wherein R1 to R4 each represents a substituent such as an alkyl group, a benzyl group, an aralkyl group, etc. Each represents a substituted or unsubstituted alkyl, alkenyl or aryl group.
Representative compounds include the following: 
(7) Phenylamine Series Compounds
Phenylamine series compounds include, for example, those represented by the general formula below.
xe2x80x83Arxe2x80x94NHxe2x80x94R6 
wherein Ar represents an aryl group, and R6 represents a substituent such as an alkyl group, an aryl group, a benzyl group, etc.
Representative compounds include, for example, the following: 
As preferred antioxidants, those having a hindered-phenol group in the molecule are advantageous in terms of the stability of a coating composition, properties of a photoreceptor repeatedly employed, and potential stability. A mixture consisting of different types of antioxidants may be employed.
In order to secure the storage stability of the solvent and repeated properties of electrophotography, the added amount of antioxidants is preferably between 20 ppm and 5 percent and more preferably between 50 ppm and 3 percent of a coating composition. The added amount is preferably between 0.001 and 10 percent and more preferably between 0.01 and 5 percent of the solid portion of the dried coating layer.
In order to improve durability, a non-photosensitive layer, such as a protective layer, other than the photosensitive layer may be provided, if desired. The above-mentioned charge transport material is incorporated into this layer and a photoreceptor comprising a so-called plural layer type charge transport layer may be prepared.
In order to constitute the surface layer of a photoreceptor, physical property improving agents (such as silicon atom- or fluorine atom-containing binder resin, fine organic particles and/or fine inorganic particles) are incorporated into the above-mentioned protective layer or upper charge transport layer, of a plural-layer type charge transport layer, and dioxolan or a dioxolan derivative of 0.001 to 10 weight percent is retained in the same as in the case for a photoreceptor having two layers, prepared by coating a charge transport layer on the above-mentioned charge generating layer. By such constitution, the photoreceptor exhibits excellent cleaning properties and wear resistance.
Furthermore, in addition to these, spectral sensitivity correcting dyes may be incorporated into the photoreceptor of the present invention. Additives such as antioxidants, etc. may be incorporated into the photoreceptor in combination with these.
There are various methods to coat a photosensitive composition to form a photoreceptor. Specifically, a circular amount controlling type coating device, especially a slide hopper type coating device, is preferable. These techniques are described in each of Japanese Patent Publication Open to Public Inspection Nos. 58-189061, 8-318209 or 9-10654.
((Subbing Layer, Support))
Furthermore, when a subbing layer is provided, a resin-based subbing layer employing polyamide series compounds such as nylon, etc., or a so-called ceramic based subbing layer (referred to as a hardened subbing layer) employing an organic metal compound, and silane coupling agents is preferably employed.
Still further, employed as conductive supports for the above-mentioned photosensitive layer, may be a metal plate or metal drum composed of aluminum, nickel, etc., plastic film or a plastic drum spattered with aluminum, tin oxide, indium oxide, etc., or paper, plastic film or a plastic drum coated with a conductive material.
The present invention is explained with specific reference to examples. However, the embodiment of the present invention is not limited to the examples.